The muscles in the lower spinal ("paraspinous") area (the lower thoracic, lumbar and sacral portions of the spine) and the corresponding spinal joints represent a portion of the human body which in an adult is frequently the cause of discomfort. In many cases this is due to lack of exercise of and postural strain on those muscles and joints. The common play activities of children, which include significant amounts of stretching, bending and other movements of the trunk, keep the paraspinous muscles and joints limber. The relatively sedentary activities of adults, however, include few of such movements, so that the muscles and joints become much stiffer and movement becomes limited and often painful. For instance, when a person unaccustomed to such work spends a spring weekend strenuously preparing a back yard garden by doing extensive digging, hoeing, raking and the like, he puts considerable stress of the paraspinous joints and muscles. The next day the person finds that his lower back area is extremely sore and movement is difficult. Similarly, when a person engages in sports activities such as golf or tennis which require considerable spinal motion, he may suffer resultant lower back pain and restricted movement even if he is accustomed to such activity. These types of problems could be overcome and prevented if there were means available to exercise the paraspinous muscles and joints in an effective manner.
Pain in the lower spinal region and restricted movement may also occur from injury or unexpected stress to the region. It is commonly found that under such conditions muscles go into spasm, which can be defined as involuntary contraction. Under such conditions the person suffers pain and restricted motion, and cannot overcome the spasms because the muscles are not subject to his voluntary control. It is often very difficult to reduce or eliminate the spasm and alleviate the pain and restriction of motion.
There have in the past been a number of devices designed to provide exercise to the lower spinal region In these devices the user stands or sits in a predetermined position and then goes through bending and twisting motions. While these devices can be useful to provide exercise to one who is already reasonably fit, it is commonly found that those who need exercise to overcome muscle and joint pain and stiffness due to prior inactivity or muscle spasm find the devices difficult and painful to use. In many cases the pain resulting from use of the machines is so great that the user cannot continue the exercise.
In addition, many of these prior art machines must be manipulated by the user against resistance. The devices, therefore, provide no help for a person who is unable to move his lower spinal region, but who would benefit from such motion induced by external means. This is typically the case when a person suffers muscle spasm.
All of such devices also force the user to move or exercise in an environment where the spine is under significant axial loading induced by gravity. This causes the facet joints to be more closely interlocked and therefore additional muscular effort is required to move the lower spine. The problem is compounded if the person also suffers with any degree of arthritis. The additional muscular effort needed to overcome the gravity loading has two adverse effects: it prevents the healthy user from obtaining the maximum muscle and joint movement since a portion of the person's muscular effort is wasted in overcoming the gravity loading, and it further inhibits the motion of those who already have restricted motion. It can also induce pain or increase the amount of pain already present. Consequently, the conventional exercise machines are limited in a degree to which they can provide effective lower spinal motion.
It has been known that a person's body can be placed in a position in which there is little or no axial gravity loading of the spine. For instance, a person lying horizontally prone or supine has the spine in an essentially unloaded position. In such a position, however, one cannot by himself perform effective exercise of the lower spinal region and there are, to our knowledge, no machines which can effectively assist him. Similarly, a degree of gravity unloading of the spine can be provided by applying traction while the person lies generally horizontally, as occurs in a traction arrangement called "semi-Fowler position". However, the person in traction cannot perform effective movement or exercise of the lower spinal region.
There have been devices intended to provide an approximation of a human adult crawling motion. One such device, of European origin, utilizes two parallel tracks oriented axially of the user's body. The user kneels in a crawling position with his hands and knees resting on wheeled supports mounted on the tracks. The user can then move hands and knees forward and backward in a straight line parallel to the axis of the body. Because the axially oriented tracks constrain any other motions, however, there is no significant movement of the lower spinal region, particularly the truncal muscles and spinal joints, since all movement occurs at the hip and shoulder joints. Another such device is illustrated in U.S. Pat. No. 4,324,399.
It would therefore be of significant value to have available a device which would enable a user to obtain the maximum degree of motion of the paraspinous muscles and joints. Healthy users could obtain optimum strengthening of the lower spinal region while those with limited movements and/or pain could lessen or eliminate the pain and improve the degree of available motion.